Hydraulic shock absorber



Feb. 27, 1940.

E. F. ROssMAN ET AL HYDRAULIC snoek ABsoRBER Filed Oct. 28, 1938 ATTORN EY5 Patented Feb. `27, 1940 uN-irED- stares 2,191,942 HYDRAULJC SHOCK Ansonsten Edwin F. Rossman, Dayton, Ohio, and Henry 0. Fuchs and Robert B. Burton, Detroit, Mich., assignorsto General Motors Corporation, Detroit, Mich., a corporation of Delaware Application october 2s, 192s, seri-a1 No. 237,400

4 Claims.

This invention relates to improvements in hydraulic shock absorbersy particularly adapted to 'control' the 'approaching and separating movements of the frame and axles of a vehicle.

j ,It is among the objectsk of the present invention to provide a double acting hydraulic shock yabsorber offsimple and compact structure and which is capable of controlling the relative move- 1 ments of a vehicle frame and axles to a predeysuch movements. i Further objects and advantages of the present inventionv will be apparent4 from the following` l description, reference being had to the accompanying drawing wherein a preferred embodiment of one'v form of the present invention is clearly shown.

'Inthe drawing:l Figure 1 shows'a shock absorber embodying 2Q the present invention, applied to a vehicle frame and axle, both of which are lshown iniragmentary form; i v

Figure 2 is a longitudinalv sectional view taken through. the shock absorber,` certain parts thereof beingshown in elevation for the sake of clearness; and f `Figure' 3 is a detail fragmentary view in section, taken along the line 3--3 of Figure 2.

" ,R'eierring tothe drawing, the numeral 2B des-y 39 ignates,in fragmentary form, the frame of the vehicle to which thel shock absorber is attached. The vehicle axle designated by numeral 22, carries vehicle springs 23,`which are hingedly secured to thevehicle frame 2li in the usual manner. These hinged connections vare not shown in the present drawing. v

The shock absorber 2l comprises a housing 25, the open end of which may. be closed by a cap 25 secured to the casing vby screws 2l. This casing 25l provides two cylinders 35 and Slin' substan-` tiallyparallel relation, these cylinders being separated by the inner Walls 32 and 33 respectively. The ends of the cylinders more adjacentv the cover plate 25 of the casing are open, communi-y 45. catingwith whatmay be termed the reservoir portion Sil of the casing.- ldiri-the casing are provided two vrecesses. 35. and, opening to the eX- teriorA oi. the casing, the outer ends ofrthese rel cesses being interioriy threaded `to receive screw caps 3l and 3S respectively. .These recesses 35 and 3E may be termed valve chambers. Valve chamber 35 is in communication with the cylinder 3U by a duct 35. 4A counterbore M in the recessA 35 provides an annular ridge forming valvei seat '40. .Thiscounterborelfisfin communicavtermined degree throughout the entire range of' y the numeral 5D, the piston in cylinder 3l by the the piston head by a spring 53, interposed bev tion With the cylinder 3lthrough the passage 42. An extension of the duct 35 beyond the valve chamber 35' communicates with valve chamber 35 and forms the valve-seat` 45. An opening in the bottom of the cylinder 3l designated Vby the numeral 46 Vprovides communication between valve chamber :vii and the cylinder 3|.I Each valve chamber 35 and 36 has a spring-loaded check-valve, the check-valve of chamber 3 5 being designated by the numeral Ell. The spring which 'urges the valve 58 upon its seat 4Q, to close the counterbore portion 4l from the valve chamber 35, is designated bythe numeral 5|. The valve 52 in the chamber lil-lk is urged by its spring 53 upon the'valve-seat 45, normally to shut oiic communication between the valve chamber 35 andA the valve chamber 36. "Each cylinder 3i! and 3l is provided with a piston, the one in `cylinder 30 being designated by numeral 6l. '.Both of these pistons are identical and, therefore,l onlyon'e oi them will be described detailedly. Piston 55 has a head portion whose outer surface 62 is sloping', as shown in Figure 2; Apassage 53 through the piston head provides 25 communication between the chamber within the cylinder formed by the piston Stand the reservoir chambery! 'of the casing. About the. mouth of this passage B3 more adjacent the interior oiv the cylinder there is provided an annular valveseat A65 upon whichthe disc-valveiit is yieldably urged by a spring 51, interposed between the disc valve and the cage t8. This cage 58 is maintained in position upon the interior surface of tween the piston and the bottomend wall of thev cylinder 30. ,Normally this spring 'urges the piston 8B toward the open end of the cylinder 3U and into ,engagement with its actuator. A recess in the sloping surface 52 oi the piston 6D receives 40 the shank portion .of a Wear piece 'It whose outer surface is parallelfto and thus slopes similarly to the outer surface 52` of the piston. The valve i501? the piston 6i is identical With the valve 56 ofthe piston Gil; springl i5 urges piston 5I into engagement with its/actuator and piston 5l', like piston Gil, has asIOping head. surface provided with awear piece 8E! similar to wear piece 'i0 on me piston su. 50

A shaft 9D is supported by and journaledin casing 25, one endof said shaft extendingto the exterior of they casing and having the shock absorber operating arm `9| secured thereto` This arm y91` yis secured to the axle 22 of the vehicle by a link 92 and thus any movement of the axle 22 will Abe transmitted to the arm 9|.

Within the casing 25, shaft 90 carries the actuator cam which, as shown in Figure 2, has two oppositely disposed arm portions |0| and |02. Arm |0| extends into the path of piston 60 and is thus engaged by its wear piece while the otherarm |02 of the operating cam 00 extends into the path of the piston 6|' and is consequently engaged by its wear piece 80. Each arm is provided with a convex curved surface, the one of the arm |0| being designated by the numeral while the convex curved surface of arm |02 is designated by the numeral 202.

It will be noted that the center of shaft 90 lies in a plane parallel to and passing midway between the axis of the cylinders 30 and 3|.`

From Figure 2 it will be apparent that if the sloping surfaces of the two piston heads were extended so as to intersect such intersection would take place substantially on the plane passing midway between the cylinders and through the center of the shaft 90 and at a point intermediate the center of said shaft 90 and the closed end of the casing including the valve passages.

The convex curved surfaces 20| and 202 of the respective arms 10| and |02 of the actuator cam |00 are so designed that they will effect movement of their respective pistons a predetermined` or selected distance for each degree of movement of cam 90 throughout its entire range of travel` In the present drawing these convex curves are shown to be of such a charwithin the casing.

acter that the respective pistons will be moved 'substantially an equal distance for each degree of rotation of the operating cam throughout its entire range of travel within the casing. Thus the pistons will displace an amount of fluid per degree of cam movement as said cam approaches the extreme end of its range of movement, equal to the fluid displaced by the piston per degree of cam movement when saidcam is in or adjacent to the vertical or normal position, in which position the cam is shown in Figure 2 of the drawing.

- With an ordinary link connection between the cam and pistons or a ilat surface contact therebetween it may readily be seen that the pistons would be moved a greater distance per degree of l travel of the cam adjacent its vertical position than per degree of travel of the cam near its eX- treme' end positions for as the cam approaches f a position 90"` from that shown in the drawing its effective horizontal movements upon the pisof the pistons 50 and 0| within their cylinders as i ton are materially reduced and thus the pistons would displace a greater amount of iuid in one range of cam movement than in another. In fact the fluid displacement would be a variable throughout.

* The cam surfaces 20| and 202, as shown in l Figure 3, are comparativelyl broad and due to their contact under pressure of springs (i9 and T9, with the inclined surfaces of wear pieces 1U and 80 on pistons 60 and t! respectively, any rotation y cylinder 30.

the axle 22 is thrust upwardly to approach the frame 20 of the vehicle. `Due to connectionswith y `the operating arm 9| this arm Vwill consequently be moved in a clockwise direction as regards the drawing and thus the cam v|00 will besimilarly rotated. Spring 69 will cause piston 60 to follow` the clockwise movement of the cam arm |0| and consequently fluid in the reservoir will move the valve 69 against theeifects cfg-its spring 61 permitting the necessary substantially unrestricted fluid flow from the reservoir 34, throughpiston passage 63 into kthe displacement vchamber of This discharge of fluid under pressure from the displacement chamberl' into displacement chamber will exert vpressure upon the inner surfaces of thepiston-'Bil and thus will assist the spring 69 in maintaining thewearpiece l0 of this piston in engagement withthe cam` Likewise fluid pressure from displacearm |0|. ment chamber 30 into` 3| will assist spring 19 in maintaining the wearpiece 80 of piston 6| in engagement withl the cam arm |02.

This clockwise movement of cam itsv arm |02 to exert la pushing. forceupon the piston 6|, therefore exerting a pressure upon the incompressible iluid within the displacement chamber of cylinder 3|. beneath saidpiston 6|. Pressure upon this iluid in chamber .3| willbe transmitted upon the valve 5|) to rmove it against the effect of spring 5| from the seat 40 .thereby to establish a fluid flow pastI valve into the valve chamber 35 and thence through'the passage or duct 39 into the cylinder 30. lValve 50L will offer a restriction to the fluid flow froml chamber 3| to chamber 30 and this consequent restriction to fluid flow will resultr in the shock absorber offering a resistance tothe approaching movement of the axle 22 toward the' frame 20.

The above described movement of the axle 22 will compress the vehicle spring 23, which, after.'

cessationof the upward thrust will rebound toward its normal load `position resulting in a sepi-V arating movement between the frame 20 and the axle 22 of the vehicle. y Now a reverse movement of the shock absorber obtains and consequently the cam |00 will be rotated counter-j clockwise causing the piston lto be pushed into its cylinder against the effect of spring 09 and the piston 6| to move out of its cylinder followingy the counterclockwisemovement ofthe cam arm |02. Under these conditions an unrestricted iluid flow will be established from the reservoir 34 through the passage of the piston 6|-` and past its valve l5 and into the 'iluid displacement'chamber of cylinder 3| beneath the piston 6|. The pressure exerted upon thev iluid' in chambery 30 by the inward movement of piston 60 will cause valve 52 to be moved from its seat 45 to permit aL restricted uid flow from displacement chamberv 30 to displacement chamber 3|. As before, this restriction to the uid ow will result in the shock absorber oiTering resistance to the sepa-k rating movement of theframe and axle ofthe vehicle. v

The present shock absorber has an end-to-end b5..

discharge,that is, `one displacement chamber discharges its fluid under'pressure directlyinto the opposite displacement chamber, and'therefore it will be readily seen that the movement of the two pistons must be equal as Well as theirdisplacement for, if vone chamber would discharge 1 fluid faster than another, an unbalanced condition would obtain, necessitating iiuid to be forcedout through leakage paths around the pistons.

However, if bothy pistons -displace fluid equally,'

the present instance these convex .curves are soA designed that eachy piston will be moved a like distance per degree of cam movement at either the neutral or central position of the cam or as the cam approaches its extreme end positions'. It 'may also be understood that these convex curves may be so designed that a greater or lesser movement per degree of cam travel may be transmittedl to the piston at either the extreme end positions thereof or at the normal central position. 'The broad -flat contact of the operating cam'armswith the sloping Wear pieces of the respective pistonsi prevents piston rotation which is necessary in the present instance where vboth pistons vare cut away on one side to permit a closer approach to the operating cam. rlhis particular arrangement of the shock absorber casing and its parts, particularly the substantially parallelrelationship of the two cylinders, the partial nestingof the pistons with the cam at certainpositions and the designv of the peculiar shaped cam permit a compact structure which is greatly desirable, particularly when shock absorbers are to be used in the present day vehicle where numerous other parts upon the frame of the vehicle reduce available space.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed `is, as follows:

1. Ahydraulic shock absorber comprising Ain combination, a casing providing two cylinders in substantially parallel relation and in communication with each other through valved ducts; a piston in each cylinder, each piston having a slop-ing head portion oblique relative to its axis and means adapted to provide for the transfer of fluid fromone side of the piston to the other; a

'shaft in said casing; a cam carried by the shaft,

said cam having identical, oppositely disposed arms each provided with a curvedportion engagz ing the head of a respective piston, the slope of which opposes rotation of the piston in the cylinder as it is moved by the cam; and a Aspring urging each piston into engagement with its respective cam arm.

2. A hydraulic shock absorber comprising in' combination,`a casing providing two, substantially parallel cylinders; a piston in each cylinder, the

head portion of each piston being oblique relative .f

to the piston axis; a cam rotatably supported within the casing and having oppositely disposed arms each provided with a curved portion engaging a piston head and adapted to aotuate the respective pistons ka predetermined, substantially equal distance for each degree of cam rotation throughout its range of movement within the casing; and a spring urging each piston against itsv respective cam arm.

'3. A hydraulic shock absorber comprising in combination, a casing providing two cylinders substantially in parallel relation and vaived ducts connecting them; a piston in each cylinder, each pistonhaving a head portion oblique to the plane of piston movement and provided with means for transferring uid from one side of the piston head to the other as the piston movesin onedirection; a cam rotatably supported within the casing and having arms each voi which is adapted to engage a 'piston head to actuate said piston, each arm `having a particularly designed curved surface en'- gag'ing the oblique head of the piston whereby rotation of the piston is opposed and the piston is moved an equal distancefor each degree of cam rotationthroughout its range of movement' within the casing; and a spring urging each piston into engagement with the curved surface'of its respective cam arm.

4. A hydraulic shock absorber comprising in combination, a casing providing two cylindersin substantially parallelrelation; a cam rotatably supportedy within the casing and having an arm v extending over each cylinder opening, each arm presenting a convex surface of predetermined ,r

curvature adjacent each cylinder opening; a piston in" each cylinder, having a head portion presenting a surface oblique to the plane of piston movement engaged by the convex surface of the `respective cam arm to prevent rotation of the pistons in their cylinders as they are actuated therein; the convex surfaces of the cam arms actuating their `respective `pistons a predetermined, substantially equal distance for each degree of camrotation throughout its range of movement Within the casing; and a spring urging each piston into engagement with its respective cam arms.

EDWIN F. Rossimn.` HENRY` o. FUCHS. f lROBERT B. BURTON, 

